Thromboxane A₂ Signalling in Humans: a ‘Tail’ of Two Receptors

Since its discovery in 1975, we now have a wealth of knowledge relating to the biochemical, pharmacological and physiological actions of thromboxane A₂ (TXA₂) and its related metabolites. These molecular insights have been greatly expedited by the molecular cloning and characterization of a cDNA for the human TXA₂ receptor, now termed the T Prostanoid or TP receptor, from a megakaryocytic/placental cDNA library in 1991, and later through the discovery of a cDNA encoding a second isoform of the human TP receptor in 1994. The requirement for two TP receptors in primates, but not in other species thus far investigated, is unclear, but points to potential species-specific physiological differences. In this review, I will describe some recent advances in the research field of TXA₂/TP receptor signalling, focusing particularly on studies pertaining to the human TP receptor isoforms.